It's a funny old thing is colour. Firstly I always think it is worth a look in the BS381c colour charts as many colours ended up in a standard list of one sort or another. In this instance there is a Dark Indian Red, BS381c 448. One source of the chart is with Stephen Hull, here.
http://www.stephen.hull.btinternet.co.uk/bs381c.html This may or may not be of any use. There is also a similar list of shades in the RAL charts, and Chestnut, RAL8015 comes to mind, although being a German system, RAL is unlikely to be useful other than an interesting comparison.
There is an entry re Indian Red on Wikipedia which might of curiosity value if nothing more, here.
http://en.wikipedia.org/wiki/Chestnut_%28color%29
I say it's a funny old thing because while I have seen modellers getting very hung up about exact shades of colours, and spending ages trying to match a colour to some sample or other, and indeed it is nice to get it right; I don't dispute that; but in real life there are so many variables such that shades can change quite remarkably, and really, there is no one correct shade for many of these earlier colours. Therefore in my instance, who knows whether the sample is right in the first place even if it is an original sample?
The very quotation that the top coats are put on over other base colours, (ends over white and sides over lead), suggests that the ends and sides will look slightly different in colour as top coats are greatly influenced by the colour over which they are applied.
The actual rendition of the colour will depend on all sorts of things, such as accuracy of the original mix of the colour, initial pigment grade, which is likely to have been less controlled in the old days than it is now, actual pigment types, how old the paint is, and how affected by the sun it has been, etc. Many colours fade rapidly. It will also look different in different types of daylight, and most importantly, the distance from which it is viewed. The farther away the observer, the lighter and bluer the colour will appear. Therefore if you are modelling a vehicle which is normally viewed at a distance of say three feet, this represents about 230 feet in 4mm scale, so the colour should in theory be rendered differently for this scale distance, rather than the actual three feet distance. This may be pedantic however, but nevertheless it makes a difference!
All this can be very confusing, and in the end everything is a compromise of all the above, so as in everything, if it looks and feels right, then it probably is.